1. Field of the Invention
The present invention relates in general to a lid or cover for a container and relates in particular to a vented, watertight plastic lid of the type commonly used to cover and seal beverage containers such as disposable coffee cups.
2. Description of Prior Developments
Disposable lids for food and drink containers are typically vacuum formed from a thin sheet of thermoplastic material such as styrene plastic. Radiant heat is applied to soften the plastic material as a vacuum draws the material over one or more lid molds. When cooled, the lids are trimmed, die cut and vented. A punch is used to puncture a vent hole of about 0.020 inch in the top central region of each lid.
Such container lids or covers have been in use for many years and are commonly used to cover paper or plastic containers such as hot and cold disposable beverage cups, as well as disposable food containers such as soup bowls and the like. Although these lids generally perform satisfactorily, a long-standing leakage problem has been associated with the presence of venting holes. That is, beverage lids are typically formed with a small puncture hole for allowing communication between the ambient atmosphere and a volume of air trapped between the top surface of the liquid (or other material held within the container) and the interior or underside of the lid.
This venting and communication between the interior of the lidded container and the outside ambient atmosphere prevents the formation of a pressure above or below ambient pressure inside the container when hot liquids are being contained. The vent also facilitates the mounting of the lid on the container by relieving the initial compression of the air trapped within the container due to sealing of the lid over and within the container.
A particularly bothersome problem arises with conventional vented lids sealed over beverage containers filled with a hot drink such as coffee or tea. When the sealed container is placed in a paper bag, one or more paper towels or napkins are often placed on the lid in expectation of leakage through the vent hole.
As the bag is carried about, the hot contents of the container are splashed around thereby causing some of the liquid to escape through the vent. Over time, the napkins or towels provided over the lid become saturated and liquid begins to flow to the bottom of the paper bag. If the bag becomes soggy, it can weaken and tear under the load of the liquid in the container.
The result is often a messy spill wherein the lid is forced off the container upon impact with the ground. Any other contents of the soggy bag are typically soaked and spoiled. In the case of a hot coffee spill, clothing, furniture, carpeting, car interiors and any other surrounding surface, may be stained. Moreover, hot coffee and the like can cause scalding as it is ejected out of the container upon impact.
Accordingly, a need exists for a vented container lid which allows for the venting of air into and out of a sealed container yet which prevents the leakage of liquids through the vent.
A further need exists for such a lid which is economical to produce so as to promote its disposability.
Another needs exists for a disposable vented container lid which is particularly adapted For sealing hot beverages within disposable containers such as Styrofoam and cardboard cups and which prevents the hot contents from escaping through a vent formed in the lid.
Still another need exists for such a vented lid which prevents leakage, scalding and staining by hot liquids stored in disposable beverage containers.